Clinical Perspectives to Overcome Acquired Resistance to Anti–Programmed Death-1 and Anti–Programmed Death Ligand-1 Therapy in Non-Small Cell Lung Cancer

Immune checkpoint inhibitors have changed the paradigm of treatment options for non-small cell lung cancer (NSCLC). Monoclonal antibodies targeting programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) have gained wide attention for their application, which has been shown to result in prolonged survival. Nevertheless, only a limited subset of patients show partial or complete response to PD-1 therapy, and patients who show a response eventually develop resistance to immunotherapy. This article aims to provide an overview of the mechanisms of acquired resistance to anti–PD-1/PD-L1 therapy from the perspective of tumor cells and the surrounding microenvironment. In addition, we address the potential therapeutic targets and ongoing clinical trials, focusing mainly on NSCLC.     

PD-1/PD-L1 immune checkpoint: Potential target for cancer therapy

Recent studies show that cancer cells are sometimes able to evade the host immunity in the tumor microenvironment. Cancer cells can express high levels of immune inhibitory signaling proteins. One of the most critical checkpoint pathways in this system is a tumor-induced immune suppression (immune checkpoint) mediated by the programmed cell death protein 1 (PD-1) and its ligand, programmed death ligand 1 (PD-L1). PD-1 is highly expressed by activated T cells, B cells, dendritic cells, and natural killer cells, whereas PD-L1 is expressed on several types of tumor cells. Many studies have shown that blocking the interaction between PD-1 and PD-L1 enhances the T-cell response and mediates antitumor activity. In this review, we highlight a brief overview of the molecular and biochemical events that are regulated by the PD-1 and PD-L1 interaction in various cancers.     

Cytokines as potential combination agents with PD-1/PD-L1 blockade for cancer treatment

Immunotherapy has caused a paradigm shift in the treatment of several malignancies, particularly the blockade of programmed death-1 (PD-1) and its specific receptor/ligand PD-L1 that have revolutionized the treatment of a variety of malignancies, but significant durable responses only occur in a small percentage of patients, and other patients failed to respond to the treatment. Even those who initially respond can ultimately relapse despite maintenance treatment, there is considerable potential for synergistic combinations of immunotherapy and chemotherapy agents with immune checkpoint inhibitors into conventional cancer treatments. The clinical experience in the use of cytokines in the clinical setting indicated the efficiency of cytokine therapy in cancer immunotherapy. Combinational approaches to enhancing PD-L1/PD-1 pathways blockade efficacy with several cytokines such as interleukin (IL)-2, IL-15, IL-21, IL-12, IL-10, and interferon-α (IFN-α) may result in additional benefits. In this review, the current state of knowledge about PD-1/PD-L1 inhibitors, the date in the literature to ascertain the combination of anti-PD-1/PD-L1 antibodies with cytokines is discussed. Finally, it is noteworthy that novel therapeutic approaches based on the efficient combination of recombinant cytokines with the PD-L1/PD-1 blockade therapy can enhance antitumor immune responses against various malignancies.     

免疫检查点程序性细胞死亡蛋白配体-1翻译后修饰及其在免疫治疗中的应用前景

免疫检查点程序性细胞死亡蛋白配体-1(programmed cell death 1 ligand 1,PD-L1)是一种主要表达于肿瘤细胞表面的免疫抑制性分子,其可与T淋巴细胞表面的程序性细胞死亡蛋白-1(programmed cell death protein 1,PD-1)结合,抑制T淋巴细胞的激活,发挥免疫抑...     

不同检测策略在预测非小细胞肺癌的PD1/PD-L1抑制剂临床疗效中的应用

近10年来,程序性死亡因子1(programmed death-1,PD-1)及其配体(programmed death ligand-1,PD-L1)的抑制剂在非小细胞肺癌(non-small cell lung cancer,NSCLC)的临床治疗中取得了重大突破,有望改变晚期NSCLC的治疗方式。然而,PD-1/PD-L1抑制剂在对NSCLC的治疗中需要借助有效的生物标志物以寻找受益人群(约20%～40%)。目前,临床上主要的判断标准是PD-L1的表达水平。本文综述了近年来在NSCLC中,与预测PD-1/PD-L1抑制剂疗效的PD-L1表达相关的检测方法,包括免疫组化、基于DNA/RNA水平检测、可溶性PD-L1的检测、正电子发射断层显像(positron emission tomography,PET)技术、多重免疫组化技术、流式细胞术和液体活检技术等,着重探讨了不同检测策略在评价PD-L1表达上的最新进展及应用前景,从而推动其在NSCLC免疫治疗中的临床应用。     

Fragment-based screening of programmed death ligand 1 (PD-L1)

The PD-1 immune checkpoint pathway is a highly validated target for cancer immunotherapy. Despite the potential advantages of small molecule inhibitors over antibodies, the discovery of small molecule checkpoint inhibitors has lagged behind. To discover small molecule inhibitors of the PD-1 pathway, we have utilized a fragment-based approach. Small molecules were identified that bind to PD-L1 and crystal structures of these compounds bound to PD-L1 were obtained.     

Immunotherapy against programmed death-1/programmed death ligand 1 in hepatocellular carcinoma: Importance of molecular variations,cellular heterogeneity,and cancer stem cells

Hepatocellular carcinoma (HCC) is a heterogeneous malignancy related to diverse etiological factors. Different oncogenic mechanisms and genetic variations lead to multiple HCC molecular classifications. Recently, an immune-based strategy using immune checkpoint inhibitors (ICIs) was presented in HCC therapy, especially with ICIs against the programmed death-1 (PD-1) and its ligand PD-L1. However, despite the success of anti-PD-1/PD-L1 in other cancers, a substantial proportion of HCC patients fail to respond. In this review, we gather current information on biomarkers of anti-PD-1/PD-L1 treatment and the contribution of HCC heterogeneity and hepatic cancer stem cells (CSCs). Genetic variations of PD-1 and PD-L1 are associated with chronic liver disease and progression to cancer. PD-L1 expression in tumoral tissues is differentially expressed in CSCs, particularly in those with a close association with the tumor microenvironment. This information will be beneficial for the selection of patients and the management of the ICIs against PD-1/PD-L1.     

Effectiveness of PD-1/PD-L1 inhibitors in the treatment of lung cancer: Brightness and challenge

Immune checkpoint inhibitors(ICIs), especially inhibitors of the PD-1/PD-L1 axis, have significantly affected the outcomes of patients with lung cancer. Nivolumab and pembrolizumab have been approved as PD-1 blocking antibodies, whereas atezolizumab, avelumab, and durvalumab are approved as PD-L1 blocking antibodies by the United States Food and Drug Administration. However, which patient may benefit the most and how to identify patients at risk of primary or acquired resistance has not been completely defined. Meanwhile, close attention has been paid to the ongoing international and domestic clinical trials in Chinese patients with lung cancer. This review aimed to provide deep insight into the effectiveness of PD-1/PD-L1 inhibitors in patients with lung cancer, including the current settings for varied disease status, the predictive biomarkers, the resistance to ICIs,and the ongoing clinical trials in Chinese patients.     

Transforming growth factor-β signalling in tumour resistance to the anti-PD-(L)1 therapy: Updated

Low frequency of durable responses in patients treated with immune checkpoint inhibitors (ICIs) demands for taking complementary strategies in order to boost immune responses against cancer. Transforming growth factor-β (TGF-β) is a multi-tasking cytokine that is frequently expressed in tumours and acts as a critical promoter of tumour hallmarks. TGF-β promotes an immunosuppressive tumour microenvironment (TME) and defines a bypass mechanism to the ICI therapy. A number of cells within the stroma of tumour are influenced from TGF-β activity. There is also evidence of a relation between TGF-β with programmed death-ligand 1 (PD-L1) expression within TME, and it influences the efficacy of anti-programmed death-1 receptor (PD-1) or anti-PD-L1 therapy. Combination of TGF-β inhibitors with anti-PD(L)1 has come to the promising outcomes, and clinical trials are under way in order to use agents with bifunctional capacity and fusion proteins for bonding TGF-β traps with anti-PD-L1 antibodies aiming at reinvigorating immune responses and promoting persistent responses against advanced stage cancers, especially tumours with immunologically cold ecosystem.     

做客肿瘤细胞的免疫检查点分子:不在其位,也谋其政

免疫检查点是一类表达在免疫细胞表面的抑制性受体分子,对维持免疫系统的稳态发挥重要的作用。近年来,陆续发现了一些重要的免疫检查点分子,例如CTLA-4和PD-1,也能在某些类型的肿瘤细胞中表达,这些“异位”表达的检查点分子被称为“肿瘤细胞固有免疫检查点分子”。虽然目前学界对它们的认识仍非常有限,但是已有证据表明,肿瘤细胞固有免疫检查点分子在表达上存在异质性,在功能上存在多样性。特别是其通过“获得性免疫非依赖”方式调控肿瘤细胞命运现象的发现,对个体化肿瘤免疫治疗方案的设计、新型抗肿瘤策略的开发都具有潜在的意义。本文概述肿瘤细胞固有免疫检查点分子的研究历程,并重点以CTLA-4和PD-1为代表,展开对肿瘤细胞固有免疫检查点分子生物学功能和分子调控机制的论述和探讨,最后对该领域存在的科学问题和未来研究方向做一展望。本综述旨在介绍和推动“肿瘤细胞固有免疫检查点分子”领域的研究。     

Checkpoint blocking antibodies in cancer immunotherapy

Cancers can be recognized by the immune system, and the immune system may regulate and even eliminate tumors. The development of checkpoint blocking antibodies, such as those directed against cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death 1 receptor (PD-1), have demonstrated significant recent promise in the treatment of an expanding list of malignancies. While both CTLA-4 and PD-1 function as negative regulators, each plays a non-redundant role in modulating immune responses. CTLA-4 attenuates the early activation of naïve and memory T cells. In contrast, PD-1 is primarily involved in modulating T cell activity in peripheral tissues via interaction with its ligands, PD-L1 and PD-L2. Unfortunately, not all patients respond to these therapies, and evaluation of biomarkers associated with clinical outcomes is ongoing. This review will examine the efficacy, toxicities, and clinical development of checkpoint blocking antibodies, including agents already approved by the US Food and Drug Administration (anti-CTLA-4, ipilimumab) or in development (anti-PD-1, PD-L1). Future studies will likely uncover new promising immunologic checkpoints to target alone or in combination with other immunotherapeutic approaches, chemotherapy, radiotherapy, and small molecules.     

全球PD-1/PD-L1单克隆抗体市场竞争格局

目的:从产品开发角度分析PD-1/PD-L1单克隆抗体的发展现状和未来趋势。方法:检索科睿唯安(Clarivate Analytics)的Cortellis数据库的数据,利用定量分析法和对比分析法对检索结果进行分析。结果:目前已有5种PD-1/PD-L1单克隆抗体上市、4种PD-1/PD-L1单克隆抗体处于预注册及6种PD-1/PD-L1单克隆抗体处于临床Ⅲ期,未来市场上的PD-1/PD-L1单克隆抗体将呈现快速增长趋势。此外,PD-1/PD-L1单克隆抗体的商业交易也越来越多,目前共发生包括药物开发及商业化许可、专利资产出售及早期药物研发合作等10余起交易,其中药物开发及商业化许可是最主要的交易模式。结论:虽然PD-1/PD-L1单克隆抗体市场尚处于起步阶段,但随着未来技术的不断发展改进,相信未来有更多的PD-1/PD-L1单克隆抗体上市,为癌症及其他疾病的治疗提供新的契机。     

Establishment of peripheral blood mononuclear cell-derived humanized lung cancer mouse models for studying efficacy of PD-L1/PD-1 targeted immunotherapy

ABSTRACT

Animal models used to evaluate efficacies of immune checkpoint inhibitors are insufficient or inaccurate. We thus examined two xenograft models used for this purpose, with the aim of optimizing them. One method involves the use of peripheral blood mononuclear cells and cell line-derived xenografts (PBMCs-CDX model). For this model, we implanted human lung cancer cells into NOD-scid-IL2Rg?/? (NSI) mice, followed by injection of human PBMCs. The second method involves the use of hematopoietic stem and progenitor cells and CDX (HSPCs-CDX model). For this model, we first reconstituted the human immune system by transferring human CD34+ hematopoietic stem and progenitor cells (HSPCs-derived humanized model) and then transplanted human lung cancer cells. We found that the PBMCs-CDX model was more accurate in evaluating PD-L1/PD-1 targeted immunotherapies. In addition, it took only four weeks with the PBMCs-CDX model for efficacy evaluation, compared to 10–14 weeks with the HSPCs-CDX model. We then further established PBMCs-derived patient-derived xenografts (PDX) models, including an auto-PBMCs-PDX model using cancer and T cells from the same tumor, and applied them to assess the antitumor efficacies of anti-PD-L1 antibodies. We demonstrated that this PBMCs-derived PDX model was an invaluable tool to study the efficacies of PD-L1/PD-1 targeted cancer immunotherapies. Overall, we found our PBMCs-derived models to be excellent preclinical models for studying immune checkpoint inhibitors.     

N6-methyladenosine RNA modification in PD-1/PD-L1: Novel implications for immunotherapy

Cancer immunotherapy has been shown to achieve significant antitumor effects in a variety of malignancies. Out of all the immune checkpoint molecules, PD-1/PD-L1 inhibitor therapy has achieved great success. However, only some cancer patients benefit from this treatment strategy owing to drug resistance. Therefore, identifying the underlying modulators of the PD-1/PD-L1 pathway to completely comprehend the mechanisms of anti-PD-1/PD-L1 treatment is crucially important. Recent research has validated that m6A modification plays a critical role in the PD-1/PD-L1 axis, thus regulating the immune response and immunotherapy strategies. In this review, we summarized the latest research on the regulation of m6A modification in PD-1/PD-L1 pathways in cancer proliferation, invasion, and prognosis based on different kinds of cancers and discussed the possible mechanisms. We also reviewed m6A-associated lncRNAs in the regulation of the PD-1/PD-L1 pathway. More importantly, we outlined the influence of m6A modulation on anti-PD-1 therapy and m6A-related molecules that could predict the curative effect of anti-PD-1/PD-L1 therapy. Further studies exploring the definitive regulation of m6A on the PD1/PD-1 pathway and immunotherapy are needed, which may address some of the current limitations in immunotherapy.     

Revisiting PD-1/PD-L pathway in T and B cell response: Beyond immunosuppression

The regulation of T cell response depends on co-inhibitory pathways that serve to control immune-mediated tissue damage and resolve inflammation by modulating the magnitude and duration of immune response. In this process, the axis of T-cell-expressed programmed death-1 (PD-1) and its ligands (PD-L1 and PD-L2) play a key role. While the PD-1/PD-L pathway has received considerable attention for its role in the maintenance of T cell exhaustion in cancer and chronic infection, the PD-1/PD-L pathway also plays diverse roles in regulating host immunity beyond T cell exhaustion. In this review, we will discuss emerging concepts in co-stimulatory functions of PD-1/PD-L pathway on T cell- and B cell response and explore the potential underlying mechanisms. In addition, based on the elevated expression of PD-1 and its ligands in local inflamed tissues, we further discussed the role of PD-1/PD-L pathway in autoimmune diseases.     

The expression and immunoregulation of immune checkpoint molecule VISTA in autoimmune diseases and cancers

Immune checkpoint inhibitors (ICIs) and immunotherapy have proven to be a transformative therapy for many forms of cancer treatment. While many antibodies targeting the PD-1, PD-L1, and CTLA-4 pathways have been approved for clinical use by the FDA, it is clear that a single ICI is not sufficient to eradicate disease. ICI combination strategies are being extensively investigated to advance cancer treatment to next curative stage. Among the immune checkpoint inhibitors being actively investigated, the potential of VISTA (V-domain Ig suppressor of T cell activation), a unique B7 family member that functions as both ligand and receptor, is being actively pursued. This article summarizes the expression and immunomodulatory effects of VISTA in autoimmune diseases and cancer, and assesses its potential as an additional component of immune checkpoint cancer therapy.     

Near-infrared fluorescence-labeled anti-PD-L1-mAb for tumor imaging in human colorectal cancer xenografted mice

The expression of programmed death ligand-1 (PD-L1) in tumor has been used as a biomarker to predict the anti-PD-L1 immunotherapy response. To develop a noninvasive imaging technique to monitor the dynamic changes in PD-L1 expression in colorectal cancer (CRC), we labeled an anti-PD-L1 monoclonal antibody with near-infrared (NIR) dye and tested the ability of the NIR-PD-L1-mAb probe to monitor the PD-L1 expression in CRC-xenografted mice by performing optical imaging. Consistent with the expression levels of PD-L1 protein in three CRC cell lines in vitro by flow cytometry and Western blot analyses, our in vivo imaging showed the highest fluorescence signal of the xenografted tumors in mice bearing SW620 CRC cells, followed by tumors derived from SW480 and HCT8 cell lines. We detected the highest fluorescent intensity of the tumor at 120 hours after injection of NIR-PD-L1-mAb. The highest fluorescence intensity was seen in the tumor, followed by the spleen and the liver in SW620 xenografted mice. In SW480 and HCT8 xenografted mice, however, the highest fluorescent signals were detected in the spleen, followed by the liver and the tumor. Our findings indicate that SW620 cells express a higher level of PD-L1, and the NIR-PD-L1-mAb binding to PD-L1 on the surface of CRC cells was specific. The technique was safe and could provide valuable information on PD-L1 expression of the tumor for development of a therapeutic strategy of personized targeted immunotherapies as well as treatment response of patients with CRC.     

PD-1/PD-L1免疫检查点抗体药物制剂稳定性开发

近年来抗体药物在生物医药领域发展迅速。随着抗体疗法种类的不断增加和PD-1/PD-L1靶点蛋白结构的确证,临床上,越来越多针对PD-1/PD-L1免疫检查点的单克隆抗体药物被不断开发并应用于治疗死亡率高、治愈率低的多种癌症中。但是抗体药物制剂开发水平还需进一步提高,一方面同一靶点的抗体产品同质化严重,另一方面抗体药物的理化性质比小分子药物复杂,因此需要针对不同单克隆抗体的药物特性,筛选出适应于临床应用的稳定蛋白制剂处方。概括了不同抗体药物制剂处方成分(缓冲液成分、药物辅料)的作用,结合PD-1/PD-L1靶点介绍了抗体药物制剂稳定性开发的一般策略以及CDE相关的审评要点。